The present invention relates generally to controlling heating, ventilation and air conditioning (HVAC) systems for vehicles.
Many modern automotive vehicles now operate at times on battery power, either fully or partially. Since the range of a vehicle on battery power is generally much less than a conventional vehicle operated with a gasoline or diesel engine, the drain on the battery from particular vehicle systems becomes more significant. For example, in battery electric vehicles, extended range electric vehicles and some types of hybrid electric vehicles, the HVAC system can consume as much power as the average load on the traction motor on cold days. The HVAC cooling load can also be quite high on hot days. Either way, the drain on the battery from the HVAC load can significantly shorten the range the vehicle can travel on battery power. Thus, it is desirable to increase the electric driving range by decreasing the vehicle electrical loads where possible, without sacrificing occupant comfort and conveniences.